1. Field of the Invention
The present invention relates to a security lock mechanism for doors, gates and the like of the type employed for regulating access to secured areas, and more particularly to an improved security lock mechanism adapted both for dead lock and slam lock operation.
2. Summary of the Prior Art
Lock mechanisms for doors and gates employed for regulating access to secured areas have been the subject of many prior art patents. It is recognized in this art that any security mechanism must have the capability of assuming a dead lock position, yet also be capable of slam lock operation. The term dead lock position means literally that the door or gate is positively locked against movement in response to any force applied to the door or gate. Operation of the lock mechanism from the dead lock position to an open position normally requires the insertion and turning of key or, for remotely controlled lock systems, the energization of a solenoid which effects retraction of the locking bolt from the dead lock position.
By slam lock position, the prior art patents, such as U.S. Pat. No. 4,913,475 issued to BUSHNELL et al., refer to a locking mechanism which will permit the gate or door to be slammed to a closed position even though the locking bolt is positioned in its locking position. Slam locking is generally accomplished by a camming action exerted on the locking bolt by the striker plate. The conventional mechanism provide a camming surface on either the striker plate or the locking bolt which is engaged by contact of these two elements to exert a retraction force on the locking bolt sufficient to permit the gate or door to reach its closed position, whereupon the locking bolt resumes its extended position to lock the door or gate in the closed position.
The locking mechanism of the prior art have predominately involved complex mechanical linkages, particularly when a remotely controlled solenoid is incorporated in the locking mechanism. Such linkages are subject to wear and have a relatively short life when employed on a door that is frequently locked and unlocked. More importantly, prior art locking mechanisms are subject to failure to shift to an open position when any significant force is applied to the door which the lock mechanism is securing, whether that force be a lateral, or a vertical force. As is well known, locking systems used in jail cells are particularly subject to this type of abuse by the occupant arbitrarily applying a lateral or vertical force to the door at the time that the locking mechanism is being remotely operated by a guard who cannot readily ascertain that the prisoner is attempting to foul up the operation of the lock. Lateral forces on the door as low as 15 lbs. have been found to completely bind up many conventional cell door locking mechanisms and prevent unlocking. This is a serious defect in prior art mechanically operated locking systems. If one or more panic stricken individuals seek to escape through the locked door, they will kick, and push laterally on the door with sufficient force to bend the locking mechanism and prevent the unlocking and opening of the door.
Pneumatic operation of a locking system has been proposed in U.S. Pat. No. 4,691,948 issued to AUSTIN, JR. et al. Such locking system uses compressed air and a solenoid controlled valve to effect movement of the locking bolt to and from a locking position with respect to a striker plate. This system is, of course, subject to immediate failure in the event that pressured air becomes unavailable for any reason. In such event, resort must be had to a key to manually effect the movement of the locking bolt to and from its locked and open positions.
In remotely controlled locking systems, it is highly desirable that a reliable indication be provided as to whether the locking bolt is positioned in its extended locked position or its retracted, unlocked position. A variety of mechanisms have heretofore been proposed to accomplish this objective, but none have provided a highly reliable yet economical system for indicating the locking bolt position.
There is, therefore, an established need in the field of security lock systems for a locking arrangement that will successfully operate even when very substantial lateral or vertical forces are applied to the locked door or gate. Moreover, a locking system is required for remote operation which does not rely upon the existence and proper operation of a source of pressured air.